RFR: 8256827: C2: Avoid reallocations by pre-sizing lists in post_allocate_copy_removal

[Claes Redestad]

By pre-sizing the Node_Lists created in PhaseChaitin::post_allocate_copy_removal we avoid all re-allocations. 

As lists are allocated to the size we need we might also reduce memory waste, which reduce memory used by these structures by up to 50%

Throughput wise this is also a gain and saves about 10,000 instructions per C2 compilation in SimpleRepeatCompilation.trivialMath. By using bulk clearing, avoiding redundant clearing of newly created lists and adding a shallow copy routine to Node_List we save another ~9,500 instructions per compilation in the same benchmark. This corresponds with a small but statistically significant gain:

Benchmark                                      Mode  Cnt    Score   Error  Units
SimpleRepeatCompilation.trivialMath_repeat_c2    ss   50  355.342 ± 2.069  ms/op # baseline
SimpleRepeatCompilation.trivialMath_repeat_c2    ss   50  350.705 ± 1.577  ms/op # patch

Testing: tier1-4

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Commit messages:
 - Minor cleanup
 - Merge branch 'master' of https://github.com/openjdk/jdk into postaloc_presize
 - Bulk clear/copy, avoid unnecessary clearing
 - C2: Avoid reallocations by pre-sizing lists in post_allocate_copy_removal

Changes: https://git.openjdk.java.net/jdk/pull/1370/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1370&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8256827
  Stats: 51 lines in 3 files changed: 13 ins; 14 del; 24 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1370.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1370/head:pull/1370

PR: https://git.openjdk.java.net/jdk/pull/1370